Hormonal agents alter the internal / extracellular environment. Most agents are cell cycle phase non-specific. Breast, thyroid, prostate and uterine cancers are examples of tumours that are sensitive to hormonal manipulation. With these diseases, the action of hormones or hormone antagonists depends on the presence of hormone receptors in the tumours themselves (i.e. oestrogen receptors in breast cancers). 1, 7, 11 There are individual classifications of hormonal agents:13